Can your ac cause low coolant in the reservoir?

Hello...my 99 lesabre with 54,000 miles seems to be losing coolant very slowly.I dont have any leaks that I can see and the light has never come on.But I have to refill my resevoir every 2 months or so.I think I need to put some freon in my ac system cuz its not blowing as cold as it used to.....could this be draining my coolant resevoir like this?ANother thing is that I lost the plastic cap that goes on the resevoir about 3 years ago and have since then just used ducttape over the top.....could this have something to do with it.I live in Texas and it gets VERY hot down here...thanks.

Hello...my 99 lesabre with 54,000 miles seems to be losing coolant very slowly.I dont have any leaks that I can see and the light has never come on.But I have to refill my resevoir every 2 months or so.I think I need to put some freon in my ac system cuz its not blowing as cold as it used to.....could this be draining my coolant resevoir like this?ANother thing is that I lost the plastic cap that goes on the resevoir about 3 years ago and have since then just used ducttape over the top.....could this have something to do with it.I live in Texas and it gets VERY hot down here...thanks.

Replacing the antifreeze reservoir cap with duct tape? That's classic :evillol:

They do say that duct tape has one million and one uses. I just wasnt expecting that to be one of them.

If you're lucky you're antifreeze is evaporating through the duct tape. Ir like the rest of us you're upper intake manifold is very close to needing be replaced.


What year is your car?

A new reservoir cap can be purchased @ most auto parts suppliers for less than $2.00, so get a new one and remove the duct tape! The cap has a vent in it that allows pressure/vacuum to escape. When the engine cools down, the radiator will pull a vacuum and suck coolant into the radiator to fill it. In addition, if the radiator gets too hot, it will allow excess coolant to expand into the reservoir. With duct tape, these functions will be restricted! BTW, Freon has nothing to do with coolant!

If your car is not cooling then adding freon will not fix it. It may help for a while but you probably have a leak, which means that anything you add will also leak out. You need to have the leak identified and repaired to have good AC in the future. (You could also have other causes for your lack of cooling. It could be a partially clogged orifice tube, a system with moisture in it or inadequate lubricant, a faulty switch or wiring, a bad compressor, etc. But in general suspect a leak first.)

[QUOTE=persuazion]Hello...my 99 lesabre with 54,000 miles seems to be losing coolant very slowly.I dont have any leaks that I can see and the light QUOTE]

You need to check the level of coolant in the radiator when the car is cool to be sure the radiator is full. Then fill the reservoir to a particular mark. Do this with the car level and completely cool. Then a week later check the reservoir level at the same cold motor. If it's dropping, and does this over a repeat check, then you are losing coolant somewhere. It could be a seep at the hose clamps, a seeping radiator or heater core, a water pump seep, or an intake manifold that's slowly losing coolant.

The upper intake manifold can seep externally or more like leak internally and the coolant is burned through the motor until the amount increases and it causes problems that could permanently damage the motor.

So watching the level or coolant is important.

The cap on the reservoir is needed. It helps keep coolant from getting out the top but lets the air through.

The question I have is how much coolant do you have to put in over the two month period? Some evaporation is normal at the coolant reservoir especially in hot Texas! :grinyes:

IMO the reservoir cap is just there since it is the fill point and to keep debris from dropping down into the reservoir. Unless I am wrong the coolant reservoir is not sealed nor is the cap. The reservoir should have a discharge port where excess coolant from a boil over due to overheating is dumped out so there is a constant vent to the outside.

Unless there is any visible or known external coolant leaking this could be the first signs the LIM port gaskets (lower intake manifold) are going bad. This is more common on '99 and up GM cars with the SII 3800 engine over the UIM plenum or UIM gasket.

well it goes down maybe halfway between the hot and cold line in 2 months....the first time when i noticed it....the resevoir was bone dry but I dont remember when the last time I had replaced it was....I do run my ac alot and it does get to 100 degrees here often.....so I dont know if thats the problem or not....or if not having the cap on is evaporating it at a excelerated rate...I guess Ill have to get a cap and then watch it but now yall have scared me into thinking i shouldnt even be driving it til i get it looked at....how often would you normally have to refill the coolant level?

Sorry but you have to realize that the SII 3800 engine is prone to UIM and LIM gasket issues where there is a loss of coolant and all we are doing is advising you that is a possibility. Better to nip it in the bud before it gets to a bigger issue like a hydrolocked engine which could happen.

The lines between hot and cold is approximately one inch......correct? If that is the case then it could be evaporation. However, you found the reservoir empty which would be coolant loss of at least a quart or more. This is one good reason to do preventive maintenance liking checking coolant level more frequently.

I'm in El Paso where the temperatures are greater than 100 degrees and very low humidity so evaporation is probably higher. I keep the reservoir level right at the hot line when it is cold and it pretty much stays there when level is checked meaning nearly no coolant loss.

well it goes down maybe halfway between the hot and cold line in 2 months....the first time when i noticed it....the resevoir was bone dry but I dont remember when the last time I had replaced it was....I do run my ac alot and it does get to 100 degrees here often.....so I dont know if thats the problem or not....or if not having the cap on is evaporating it at a excelerated rate...I guess Ill have to get a cap and then watch it but now yall have scared me into thinking i shouldnt even be driving it til i get it looked at....how often would you normally have to refill the coolant level?
I agree, that is an excessive drop in coolant level, even for Texas! I live in “HotLanta” the weather not quite as hot, but more humid and I have not had the coolant level drop in mine at all, in the past year! You do need to have this checked out! :mad:

could the leaking gasket also cause a rough start in the morning? I have been having that lately but it goes away after it warms up.....how much will it cost to have it fixed?

Possible or it may just need a basic tune up. During startup look if you see any white colored smoke out the exhaust which would indicate coolant being burned in combustion.

Unless you are DIY capable or have the proper equipment you can get the cooling system leak down tested which may help determine if it is gaskets leaking such as UIM, LIM or head gaskets.

Do you have any sludge buildup in the coolant reservoir? Also, remove the radiator cap with engine cold and inspect the back of the radiator cap and inside the radiator filler neck. For example when the LIM gaskets start going bad you may see sludge buildup which will look like a brown greasy feeling paste which is combustion by-products and/or engine oil contamination.

theres a hose in between your mpfi and its hard to see but i've said before my mom and dad both owned pa witch is about the same. but whe your standing in front of car look in beteen mpfi it's a cooler hose for throtle body it's about 3/4 hose and about 5-6 in'' long if that it can be leaking very slow.

theres a hose in between your mpfi and its hard to see but i've said before my mom and dad both owned pa witch is about the same. but whe your standing in front of car look in beteen mpfi it's a cooler hose for throtle body it's about 3/4 hose and about 5-6 in'' long if that it can be leaking very slow.

:confused:

There is no hose for the throttle body. Just vacuum related lines. The coolant passages to the throttle body are in the UIM plenum and not visible unless you take the throttle body or UIM off. :grinno: The 60 degree GM V6 engines like the 3100/3400 do have the hoses external to the throttle body but this is not applicable to the VIN "K" or VIN "1" Series II 3800 engines.


http://i5.photobucket.com/albums/y186/lizzywiz/uim_coolant.jpg
NA SII 3800 UIM Plenum. Coolant passages to throttle body circled in red. No EGR stovepipe damage.

sorry yes 3800 never caught that diffirent because most i see is 3.8 or 3800. thanks...